What car would you rather race?

[Bill Miller]

Either a few data points have been left out or the numbers don't make much sense. Asuming the HP peaks are roughly the same, the cars shouldn't have that much difference in the torque for the same crank HP. Either Car #1 continues to make torque MUCH higher up the RPM range, or it has some hideous drive train losses to get that much difference in the torque numbers. (Or someone is playing games and running the two cars in different gears.) Based on the hints about what the real cars are, I assume it's a difference in the RPM for peak HP.

Based on that, I'd rate the two cars about even. Even HP, Car #1 weighs a little less and Car#2 has slightly better ratios and aero.

The torque numbers are misleading - they both have pretty flat torque curves (in the ranges shown - I'd like to see what car #1 has at 8000 rpm). And despite the old line about torque winning races, HP IS what counts. The other old line that rarely gets repeated "You can multiply torque, you can't multiply HP".

Tom Lyttle
[/b]

The flaw in your logic is that you're assuming that the two engines are of the same type.

[lateapex911]

Is it true then, that Otto 4 cycle, 2 cycle, and Miller engines all have different torque/hp characteristics?

I always thought that basically, HP was work produced, and was mathmatically based upon the tq numbers .

[Eagle7]

The torque numbers are misleading - they both have pretty flat torque curves (in the ranges shown - I'd like to see what car #1 has at 8000 rpm). And despite the old line about torque winning races, HP IS what counts. The other old line that rarely gets repeated "You can multiply torque, you can't multiply HP".[/b]

Agreed, but it's the area under the HP curve between the shift points that's important. And if the areas were close to the same, the flatter curve would be much preferred over one that's quite peaky.

[charrbq]

#2...horsepower this close is only a number...wt is a problem, but torque is the key...gears are almost no big deal in this case

[its66]

Either a few data points have been left out or the numbers don't make much sense. Asuming the HP peaks are roughly the same, the cars shouldn't have that much difference in the torque for the same crank HP. Either Car #1 continues to make torque MUCH higher up the RPM range, or it has some hideous drive train losses to get that much difference in the torque numbers. (Or someone is playing games and running the two cars in different gears.) Based on the hints about what the real cars are, I assume it's a difference in the RPM for peak HP.

Based on that, I'd rate the two cars about even. Even HP, Car #1 weighs a little less and Car#2 has slightly better ratios and aero.

The torque numbers are misleading - they both have pretty flat torque curves (in the ranges shown - I'd like to see what car #1 has at 8000 rpm). And despite the old line about torque winning races, HP IS what counts. The other old line that rarely gets repeated "You can multiply torque, you can't multiply HP".

Tom Lyttle
[/b]

The basic numbers actually do make sense. The crank HP on car #1 might be slightly high vs the whp/torque estimations. Torque is a measurement of force. Horsepower is a measurement of work. It is a function of torque and RPM. If an engine's torque curve is centered around a low RPM range (such as a semi-trucks diesel engine), you will have an engine which produces a relatively low HP when compared to torque. IF the engine's torque curve is skewed toward the upper end of the rev range, that engine will have a relatively high HP when compared to its torque rating(such as VTEC Honda's and certain engines with trianglular looking thingy's inside). I would estimate that Car # 1 probably has 115 lb-ft at 8000 rpm. With the numbers given, car #1's torque peak would be at approximately 6250 rpm. Car #2's torque peak would be at approximately 5100 rpm.

If you know either torque or HP at any given RPM, you can calculate the other. HP/RPM=TORQUE/5252.

[MMiskoe]

Andy - any chance of spilling what it was you were fishing for here & what the cars were?

Just curious.

[steve s]

i am guessing that car 1 would have to use a 5.1 final drive and that is a lot less losses through the driveline
car 2 would probably use a 3.7 final drive which is harder to turn so you lose more through the driveline.
car 2 with the heavy weight will not be great on a heavy braking tracks as homestead or sebring club course. also harder on tires.but then the question was which car 1 or 2 assuming both car well prepped and money was no object just winning i'll chose car 1.
p.s. remember car 2 will have the SIR to limit his hp.so he cannot make any more power . car1 on the other hand can do some more R & D and find some hidden hp somewhere in the engine.
what was the hp level of car1 2years ago ???????compared to what it makes now.??????and some engine builder are still finding more.

[its66]

I'm not so sure that the gear ratio of the differential has a measureable difference in drag(loss) through the drivetrain. Isn't the parasitic loss defined more by the design of the diff itself(bearing design, teeth shape and angle, preload, etc) I know that a Ford 9 inch rear has more loss than a chevrolet 12 bolt rear does with the same ratio. The higher (numerically) gearing does aid in multiplying torque which makes it easier for the engine to get the car rolling/accelerating.

BTW...5.12 with .757 5th gear equals 3.87(car 1)..pretty close to a 3.7 overall(car 2). The spread through gears 1-4 is a little further apart. Differential gear ratio is free. You can run any ratio you wish, so that really shouldn't even be a factor. Each racer has to make the decision which diff gear is best for his/her application. You can chose gearing for more torque multiplication at the expense of top speed, or you can gear for top end at the expense of acceleration. trade offs suck.

[steve s]

.757 5th gear is not the choise 5th gear is on car 1. there is a closer gear available.also youre right the diff multiply torque so then you're almost equal to car 2 torque wise with the 5.12 ???? then why would you run more weight in car 2 ???
at the wheel in theory car 1&2 has just about the same torque and hp ##
off the topic jim are you going to sebring this month's end hope to see you there.
carlos and myself is will to accept any penalty or adjustment scca deems necessary to level the playing field, just give us some time to do some R&D. that all we ask. let it die and wait for some results.from scca

[seckerich]

.757 5th gear is not the choise 5th gear is on car 1. there is a closer gear available.also youre right the diff multiply torque so then you're almost equal to car 2 torque wise with the 5.12 ???? then why would you run more weight in car 2 ???
at the wheel in theory car 1&2 has just about the same torque and hp ##
off the topic jim are you going to sebring this month's end hope to see you there.
carlos and myself is will to accept any penalty or adjustment scca deems necessary to level the playing field, just give us some time to do some R&D. that all we ask. let it die and wait for some results.from scca
[/b]

It is the only LEGAL option--anything you wish to share with us?

[steve s]

oops my mistake . i'll never build anything illegal. when i build car1.
and i still think car 1 is the car to build unrestricted engine is the key choice here.

[its66]

Actually, the torque multiplication is almost identical between the two cars in top gear. 3.87 vs. 3.7 is a 4% difference. Overly simplified, if you use car #2's 180 lb-ft as the standard, that effectively gives car #1 135 lb-ft. A gain of 5 lb-ft of torque. Hardly equal. If you work the same math in each gear, car #1's apparent disadvantage is lessened somewhat. Fifth gear is where the difference is most disproportionate. If car #2 uses a shorter gear to gain even more of a torque advantage, it's top speed suffers. --

I'll not only be at Sebring, I'll bring an extra 6 pack for you. Come on over. You can even bring Carlos, I'll share with him too.

FWIW, I agree that the lead time on the SIR was too short. I would think 90 day minimum, maybe longer.